The basic principals of electronic feedback carburetor systems for internal combustion engines are known and described in a number of prior art U.S. patents. See for example U.S. Pat. No. 4,252,098 granted to L. W. Tomczak et al on Feb. 24, 1981. Generally, such systems apply electronics technology to well known carburetor systems to control the fuel flow rate, the air/fuel ratio, or other parameters necessary for efficient operation of an internal combustion engine.
Such systems are designed to reduce exhaust emissions, improve fuel economy and in general obtain satisfactory operation of the internal combustion engine. Depending on system cost and operational parameters, such systems may utilize relatively crude and unsophisticated technology or elaborate and complicated technology to accomplish these objectives. However, none of the known systems provide improved fuel economy with relatively simple and inexpensive technology, while retaining accurate and reliable system operation with ready adaptation to a variety of internal combustion engines.
It is, therefore, a general object of the instant invention to provide a low cost and highly efficient control system for a feedback carburetor.
It is another object of the instant invention to provide a control system for a feedback carburetor which improves fuel economy for marine engines.
It is a still further object of the instant invention to provide improved fuel economy for a marine engine with use of minimal hardware adaptable to a wide variety of internal combustion engines.
A number of additional prior art U.S. patents are directed to control systems for internal combustion engines in which the control system automatically and continuously seeks the optimum air/fuel mixture to be supplied to the engine. Examples of such systems are shown in U.S. Pat. No. 4,368,707 to E. Leshner et al, U.S. Pat. No. 4,099,493 to Latsch et al and U.S. Pat. No. 3,789,816 to Taplin et al. The systems described in the aforementioned U.S. patents apply various techniques in optimizing the air/fuel mixture supplied to an associated internal combustion engine, but each of these references have one technique in common, that is, each of these prior art systems monitor the rate of change of engine RPM in an attempt to optimize the air/fuel mixture.
Monitoring engine RPM rate of change to optimize the air/fuel mixture is acceptable for most internal combustion engines and especially for such engines in which the RPM rate of change in indicative of engine "roughness" or other engine conditions pointing to approach of the engine lean limit. For marine engines, however, engine RPM rate of change is not an acceptable parameter to monitor in order to optimize the air/fuel mixture as the engine RPM rate of change does not necessarily indicate engine "roughness" and/or an approach to the lean limit of engine operation. This is a result of wave action in the marine environment in which the marine engine propeller is often repeatedly removed from and inserted into the water causing rapid changes in engine RPM not related to engine "roughness" and/or approach to the lean limit.
It is, therefore, a further object of the instant invention to provide a control system for a feedback carburetor which is not dependent on engine RPM rate of change.